Polarimetry task list

From RHIC Spin Group

RHIC Polarimetry Tasks

  • Longitudinal profile polarization measurement
    • In principle, the algorithm to extract the asymmetry values from a single measurement is already available
    • Need background estimation and clean up of the data coming from the head of the bunch
    • Then combine many measurements to get statistical significant result
  • Detector gain as a function of leakage current (values available, can be accessed from LogView withing the existing framework)
    • If beam conditions affect the leakage current which in turn affects the detector gains than used A_N can be corrected (if such dependence is found)
  • Polarization correlation with bunch length, intensity, 197Mhz and other cavity voltages, snake currents, etc can be studied in search for optimal settings
    • Polarization can be studied as a function of anything accessible in LogView withing the existing and well developed framework
  • Beam emittance measurement and monitoring can be done for all normal p-Carbon measurements
    • Bunch by bunch emittance monitoring is possible. It is similar to already implemented bunch-by-bunch asymmetry monitoring on both single and fill-combined measurements
  • Spin flipper studies. Polarization dependance on flipper frequencies by revolution study with fourier transform
  • There is a need for a better automated QA for p-Carbon and H-jet polarimeters
  • Estimate the amount of carbon material in the beam during the measurement. Very hard to do... need to seek for handles
  • Online analysis
    • Replacement of outdated online code and its incorporation in the common framework
    • Eventually, "online analysis" == "really fast (scaler data based) offline analysis" => Consistency among all reported values
  • Automatic H-jet measurements at injection... doesn't cost anything but can provide new information
  • Incorporate p-Carbon measurement videos in the run DB table
  • Extraction of analyzing power A_N (and A_NN) for pp and pC processes (publication)
  • DAQ upgrade with new electronics
    • Modification of online DAQ programs will be needed. The data format should be redefined for direct use with ROOT framework as it is done by many modern high energy experiments like STAR, ATLAS, CMS,...
  • AGS analysis... should have more common grounds with RHIC

Online issues

  • Target multiplexer switching. Using two horizontal (or vertical) targets in the same ring requires a travel to home position when switching the target multiplexer. The procedure is lengthy and for experts only.
  • The measurement type (sweep/fixed/ramp/emittance/...) should be saved in raw data file from the online polarControl GUI.
    Igor Alekseev: This is saved in the comment field of the REC_BEGIN record.
    Dmitri Smirnov will check if this record is useful
  • It would be nice to get control over the comment field in the polarControl GUI filled by the operator. These comments are valuable and should be saved in some way allowing us to track them down later
  • Instantaneous luminosity should be saved in raw data. What is the name of the corresponding CDEV variable?
    Igor Alekseev: The device is WCM (wall current monitor) and we save per bunch luminosities in raw data.

Things to do in offline

  • Switch to correct calibration constants for the downstream polarimeters before they were moved out of the tunnel

Check algorithm

  • Compare asymmetries, polarization profiles in AGS and RHIC at injection
  • Plot peak polarization (in the beam center at maximum intensity) as well as the average one as a function of time
  • Polarization decay... plot
  • Split pulse signal is observed in Blue-2 Downstream. There is an indication of split pulses in Yellow-2 Upstream [1] [2]
    • The generator pulse is observed in the banana in Y1D: [3]
  • In measurement 15452.205 we got three times less events in the 90-degree detectors than in the 45-degree ones. A thick vertical target 6 was used. [4]
    • The strips in the hamamatsu detectors are smaller
  • QA checks need to be revised further. A crazy measurement gives a 100 +/- 2% polarization [5]
  • The dead layer jumps for 24 to 250 GeV measurements. For example, measurements 15302.001 and 002 with B1U [6] [7]
  • Make sure the fixed target measurements are scaled and correctly accounted in the final fill polarization values
  • Need to add a histogram with the average rate per channel
  • Add empty bunch histograms to raw container
  • Consider adding a correction for the zig-zag structure seen in raw TDC [8]
  • Need to understand the step in the banana distribution [9]

Additional Thoughts

  • It would be nice to collect as much statistics per measurement as possible
    • It might be possible to estimate the desired target speed and start/stop positions for each new target
  • Targets should be used/switched systematically so that proper conclusion can be made about target survival characteristics. Also important for systematics studies